The previously accepted estimates for the areal extent (200,000 km²) and volume (325,000 to 382,000 km³) of the Columbia River Basalt Group (CRBG) have, upon reevaluation, been found to be too large. New area and volume estimates for 38 units that compose most of the CRBG indicate that it once covered an area of approximately 163,700 ± 5,000 km² and has a volume of approximately 174,300 ± 31,000 km³. Our work further suggests that the volume of individual flows is huge, on average exceeding hundreds of cubic kilometers. The maximum known volume of...